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DEVELOPMENT of hydraulic systems for the transmission of motion, force or power may he considered to have begun with the introduction of the hydraulic press, one of the great inventions that marked the Industrial Revolution during the latter half of the 18th Century. (It was patented in 1795 by the Yorkshireman, Joseph Bramah, renowned in his day for many innovations, including the beer‐engine). For many years after its introduction the hydraulic press represented industrial hydraulics.

HYDRAULIC ACTUATION of machinery has been performed for many years in a relatively modest way, but the increasing complexity of modern machinery has, of recent years, generated a greater appreciation of the virtues of this method of operation and control. The mechanical transmission of power by levers, cams and gears, might be regarded as the traditional method, but as greater demands were made for automatic operation and control, design complications became increasingly complex, and the principles of hydraulics, which had hitherto been employed only on simple presses, assumed much greater importance.

This paper aims to use this method to explore a new approach and possible technical optimal design for lubricant formulation.

The component of the developed oil was determined based on the physical and chemical properties of the base oil and the tribological properties. The analytic hierarchy process (ANP) method and SuperDecisions software were used for hydraulic oil modeling and calculation while taking performance index, work circumstance and economy into consideration.

The hydraulic oil formulation can be optimized using the ANP method, where the technical performance, economy and working circumstances of the hydraulic oils were taken into consideration in the evaluation system. The experiment analyzed and scored and screened the hydraulic oil formula in an objective and comprehensive manner.

The experiments showed that the newly developed hydraulic oils could meet the performance requirements for new energy vehicles equipped with hybrid hydraulic engines.

Apart from the basic material properties of liquid lubricants, such as, e.g., the viscosity and density of the hydraulic fluid, it is also important to have information regarding the electrical properties of the fluid used. The latter is closely related to the purpose, type, structure, and conditions of use of a hydraulic system, especially the powertrain design and fluid condition monitoring. The insulating capacity of the hydraulic fluid is important in cases where the electric motor of the pump is immersed in the fluid. In other cases, on the basis of changing the electrical conductive properties of the hydraulic fluid, we can refer its condition, and, on this basis, the degree of degradation.

The paper first highlights the importance of knowing the electrical properties of hydraulic fluids and then aims to compare these properties, such as the breakdown voltage of commonly used hydraulic mineral oils and newer ionic fluids suitable for use as hydraulic fluids.

Knowledge of this property is crucial for the design approach of modern hydraulic compact power packs. In the following, the emphasis is on the more advanced use of known electrical quantities, such as electrical conductivity and the dielectric constant of a liquid.

Based on the changes in these quantities, we have the possibility of real-time monitoring the hydraulic fluid condition, on the basis of which we judge the degree of fluid degradation and its suitability for further use.

The aim of this paper is to investigate hydraulic system performance using vegetable‐based palm oil as hydraulic fluid.

The hydraulic system performance test at different operating conditions, such as pressure, speed and oil ageing, was performed using a Yuken vane pump test rig. The endurance system performance test was also conducted for 200 and 400 h. The effect of speed on flow slip coefficient in discrete and continuous tests was studied. In discrete testing, pressure of 35 and 200 bar and speed of 750 and 1,439 rpm were used in determining flow slip coefficient. The instantaneous data were recorded in a computer using an analog‐to‐digital data acquisition system with respect to time and the parameters stored were reservoir temperature, return line temperature, suction and delivery pressures, instantaneous flow rate, total flow, total running time and torque. The obtained results were interpolated for future prediction of the system performance.

The experimental and interpolated results showed that slip coefficient decreases with increasing pump speed. The effect of aging condition on volumetric efficiency showed that the efficiency increases with aging period due to increase in oil viscosity.

This vegetable‐based palm oil could be a potentially useful substitute for mineral‐based energy transport media such as hydraulic fluid.

The investigation of hydraulic system performance using palm oil as hydraulic fluid is scarce in the literature. Therefore, the current study is quite new for the hydraulic system performance and it is hoped that it will provide a high value to researchers for further research before it can be used as hydraulic fluid.

IN MAY 1960, the predecessor of this magazine, Scientific Lubrication, published an issue devoted to the subject of “ Hydraulic Systems and Oils,” intending it to be “ … of practical and theoretical value to all readers who design, manufacture, install or maintain hydraulic equipment.” The articles were of undoubted value adding, as they did, to the store of information on hydraulic oils already published. Paradoxically, one hydraulic equipment manufacturer has recently been heard to remark that the majority of this type of literature, although issued by oil companies, gives greater descriptive coverage to the equipment than it gives to the oils. The implication was that the equipment manufacturers' greatest need was for fuller information on the oils, not the equipment.

Environmental protection regulations are becoming increasingly strict. Using water instead of a hydraulic mineral or biodegradable oil in power‐control hydraulic systems is a very positive step towards complying with these regulations. Since water hydraulics has many specifics, primarily related to lower viscosity and lubricity of water compared to oil, which greatly affects the leakage, and even more the friction and wear in these systems, a dedicated test rig is required for performing research with the real‐scale components. The purpose of this paper is to present some preliminary representative results on dynamic responses of the two hydraulic circuits with and without a mass load.

The paper presents the newly developed dedicated test rig and its dynamic characteristics when used with water and oil as hydraulic fluid. Hydraulic pressures and motions of spool and piston in the two different fluids were of special interest.

The results clearly show their dependence on friction properties of selected materials in different hydraulic fluids. While the oil valve worked perfectly, water valve has some irregularity, linked with the small gap, the shape irregularity, the surface roughness and the poorer lubrication conditions in the water hydraulics compared to the oil system.

The observed irregularity of the movement of the spool in the water hydraulic valve has almost no influence on the movement of the piston rod of the water cylinder, which is a very promising result for future research on water hydraulics.

RICHARDSON, writing in Scientific Lubrication recently, stressed the need for strict attention to the cleanliness of the fluids used in hydraulically operated automatic transmissions with special reference to storage conditions, cleaning materials and the care of filters. In the same number of the journal Chisholm briefly described methods of oil filtration in general when discussing the maintenance of industrial hydraulic systems. It will be found too that the majority of articles and booklets dealing with hydraulic fluids and systems—industrial, automotive and aeronautic—pay attention to the potential effect of impurities, their exclusion and removal, in greater or lesser detail. Similarly diagrams of typical hydraulic circuits will usually show permanent wire mesh screens or strainers in the oil reservoir on the suction side of the pump and sometimes below the filler plug while by‐pass filters are generally located at some point in the circuit after the pump. (By‐pass filters owe their popularity to the fact that should the element become completely clogged the flow of hydraulic oil is not thereby interrupted).

IN RECENT YEARS engineers concerned with the design and development of oil‐hydraulic equipment have shown an increasing thirst for information on hydraulic oils, and particularly for quantitative data on their physical properties. The following notes review the requirement for data, and the significance of the properties of closest concern to the designer.

A series of articles dealing, in as simple a way as possible, with the basic facts of lubrication, lubricants, their selection and prescription, specification, application, and testing. This series is primarily intended for students, engineering personnel who may be unfamiliar with certain aspects and others who, one way or another, are interested in this important subject.